This invention relates to deep fat fryers and in particular to a mechanical lifting assembly for commercial deep fat fryers to permit an operator to raise and lower a basket rack containing food in the fryer.
A commercial deep fat fryer typically has a tank which holds melted shortening or oil and heat tubes extending through the lower portion of the tank which heat the oil to the cooking temperature. When the oil is at a proper temperature an operator must lower the food into the tank until it is cooked and then retrieve it. Foods typically cooked in a commercial situation with a deep fat fryer include battered coated chicken, fish and non-battered coated items such a french fries. In a commercial situation it is desirable to cook large quantities of such foods, but the problem of lowering the food into the tank, and retrieving the cooked food from the tank should require only a minimum involvement of an operator. Most importantly, great physical exertion from the operator should not be required as the size and stature of such individuals will very widely from commercial establishment to establishment.
Certain commercial deep fat fryers are intended to be pressure cookers also and therefore, a heavy lid is provided. Typically the baskets of food are suspended from the lid. In such a situation as described in U.S. Pat. Nos. 5,402,712; 6,009,795; and 6,322,831 due to the weight involved, a motorized assembly is used to raise and lower the lid and depending baskets of food. The presence of a motorized assembly will involve maintenance, and the possibility of breakdowns. In the above patents, the motors are disposed in the rear part of the fryer assembly which would normally be adjacent a wall and a flue for the heat tubes. In a typical fast food establishment space is at a premium, and the back of the fryer would normally be disposed abutting a wall. Maintenance of a motor then could be difficult and time consuming. However, if the lid is very heavy, there may be no choice but the use of a motorized assembly.
In other commercial deep fat fryers the fryer itself is not a pressure cooker and the tank remains open to the atmosphere. In such fryers typically the food is disposed in baskets or on a stack of mutually spaced trays which when lowered into the fryer will occupy substantially the cooking area available. Even though a heavy lid is not involved, raising and lowering such a quantity of food could require considerable physical strength without a mechanical assist.
There is a need then for a reliable mechanical assist for raising and lowering food containing trays from a deep fat fryer which requires only average physical strength and can be operated by virtually any kitchen employee in a commercial fast food establishment.
U.S. Pat. No. 4,930,408 describes a mechanical assist wherein although a lid is utilized, the lid with a tray carriage suspended from the lower surface is mounted on a pair of arms which are secured to a vertically moveable carriage mounted at the rear of the cooker. The vertically moveable carriage is connected by cables and pulleys to a counter balancing weight which counter balances the weight of the lid. The combination of pulleys and cables is described as providing a three to one mechanical advantage. Therefore, even though when the lid is physically lowered the counter balancing weights must be raised, there is a three to one mechanical advantage to achieve the same. It is further described that two cables are provided, one active and one passive as a back up in case of failure of the active cable and/or its pulley system. This patent, however, does not describe the structure which would be optimal in the case of a mechanical lifting assembly which did not involve a heavy lid.
It has been discovered that a dependable lift assembly with a mechanical assist can be provided for deep fat fryers wherein ordinary physical strength only is required, and a basket or tray can be maintained in the raised position or in the lowered position without regard for the weight of the food therein. In other words the basket or trays would be maintained in a raised position even though it is loaded with food or in a lowered position even if it is empty. Furthermore, the mechanical assist lift assembly of this invention does not involve cables and pulleys with counter weights.
The lift assembly of this invention is designed to translate rotary motion into linear vertical motion whereby raising or lowering a lifter arm causes rotary motion about a fixed arm support coupling. The lifter arm is U-shaped with opposing ends being rotatably coupled to a support. A long axle is disposed between the rotatable couplings so that rotational movement of the handle and coupling will result in rotational movement of the long axle. A short axle is fixed above and below the long axle.
Cam members are fixed to the long axle, and extend outwardly therefrom with arms disposed in a common plane perpendicular to the axis of the long axle. Springs are attached at the ends of the cam members with one spring affixed to the upper short axle, and the opposite spring affixed to the lower short axle. Upper and lower stops are also provided for the rotational movement of the cam members.
In operation then when the basket is lowered, the springs will be placed in tension to counter act the weight of the food on the carrier and when the carrier is raised the tension will be relieved. Furthermore, spring tension and the cam action design will keep the basket in a lowered position; by equalizing the tension, at a midpoint position, or in the upper position against a stop.
Accordingly, it is an object of this invention to provide a mechanical lift assembly for a deep fat fryer to assist an operator in raising and lowering food relative to the cooking tank.
It is another object of this invention to provide a mechanical assist which uses a cam and spring action to translate rotational motion into linear motion.
It is another object of this invention to provide a cam actuated mechanical assist assembly which will maintain a food carrier in a raised position, in a midpoint position, or in a lowered position by the action of raising and lowering a lifter assembly handle.
It is further object of this invention to provide a mechanical lift assembly which utilizes springs mounted on a cam mechanism mounted on a rotatable axle to use spring tension to assist in raising and lowering a food carrier assembly.
It is yet another object of this invention to provide a spring actuated cam mechanism in combination with a rotatable stop for a lifter assembly wherein when the assembly is lowered the springs will be placed in tension and at the lowest point the cam mechanism will lock the springs in maximum tension whereby when the assembly is raised at a midpoint the springs will be in balanced tension, and at the upper point the springs will still be in tension, against a rotational stop to counter act the force of gravity on the lifter assembly.